The invention relates to a device for actuating an electrical switch, especially for the installation in the steering wheel of a motor vehicle, with one first essentially fixed contact element, and a second contact element that is moveable against a return force, and with an actuating means.
Contact actuating devices of this type have been known for some time for the actuation of the horn switch in motor vehicles. They may be used in the same way for other applications, such as for the power-assisted opening and closing of the side windows or of the sliding sunroof. In the application sector of xe2x80x9cmotor vehiclesxe2x80x9d it is important that the contact device should function reliably over a long period of time, that is, it should establish the required electrical contact only when the driver depresses the contact device, and the contact should open again when the contact device is released by the driver. This requires a secure mounting of the involved contact elements in the open position, to avoid any unintended closure of the contacts on account of vibrations occurring in the vehicle. On the other hand, the moveable contact element must not be fixed so firmly in its open position that the closure of the contact will be possible only by exertion of a considerable force. Finally the contact separations should be realizable as small as possible so that the required contact closure is not unduly delayed by a long actuation stroke which would be unacceptable especially when attempting to sound the horn.
Furthermore, the required contact device has to be produceable as simple and cost-effective as possible and has to be adaptable to different often very space-limited installation conditions.
In order to meet these partly opposing limiting conditions, a device of the above-mentioned type is proposed characterized in that, according to the invention, the contact elements consist of elongated wire or strip shaped material sections which are held parallel to one another within a spacer cage at a defined distance from each other, sections with rigidly maintained distance between the elements alternating, as seen in a longitudinal direction, with sections where the second contact element can be pressed against the first contact element by means of an actuating device accompanied by an elastic deformation of the material section of the second contact element.
The invention relies on the fact that electrically conducting materials, in particular metals, are sufficiently elastic, when present in the form of wire or strip shaped starting material, to be deformable transverse to their longitudinal extension to the extent that the defined distances between the contacts can be bridged. When such material sections are held parallel to, and at a defined distance from each other, within a spacer cage, a contact device is obtained which may be embodied within widely varying limits with respect to the actuating force, the return force and the contact separation, since not only the sections of rigid distance maintenance and the sections capable of elastic deformation, provided according to the invention, may be varied in their longitudinal extension, but the cross-section of the material sections, their material specifications and their elastic properties are also variable. The elastic return force of such material sections remains virtually unchanged over the operating times usual for motor vehicles, so that on the basis of the once chosen design dimensions for both the spacer cage and the material sections an electrical contact device can be produced whose functional parameters do not change.
The constructional design of the contact device according to the invention is very simple. It is just necessary to arrange two material sections within a spacer cage, so that at least one of the material sections is capable of being deformed transverse to its longitudinal extension to the extent that it can be pressed against the other material section when appropriately actuated. The material sections need not be further processed and require only a connection to the electrical supply system of the vehicle. The contact device according to the invention can be designed in any required length, and can therefore also be combined with actuating devices which encompass a plurality of point shaped actuators or a large-surface actuating area. The two material sections do not have to be arranged in a straight line; they may be arranged in any desired curved configuration, as long as they are bent in the same sense and are maintained parallel to and at the same distance from each other, and can be elastically deformed by the actuating device to the required extent transverse to their longitudinal extension. There is furthermore no need at all for the two material sections to have the same cross-sectional area or to consist of the same type of material. Essentially important is only that one of the two material sections is sufficiently elastic to allow it being pressed against and into contact with the other, possibly rigid, material section.